An automotive environment is traditionally considered to be a very harsh and extreme environment with respect to electrical noise, radio frequency (RF) interference, electromagnetic interference (EMI), vibration, temperature, humidity, etc. A vehicle is never considered a stationary device, thus it is always moving and subject to an environment with continually varying conditions. It is also well known and accepted in the automotive engineering society that extreme environmental conditions do exist. Considering these facts, it makes it virtually impossible to predict the nature of the environment or conditions a vehicle will be exposed to at any given moment. Therefore, to create a robust electronic control system, a system that performs favorably while subject to the worst case environments and conditions is desirable.
The inputs to an automotive system can contain mechanical switches. It is well known that mechanical switches have aging and mechanical contact bounce characteristics that can vary over time and under different environmental conditions. These mechanical switches are typically connected to the electronic controlling device through long wires. These long wires can contribute to noise on the input in several different ways. Of these ways, it is possible for the wires to act as antennas, thus coupling strong RF radiation into the controlling device. In addition, switch wires that are parallel with other wires can cross-couple inductive energy further adding to the possibilities of noise and interference. With these common factors and others taken into consideration it becomes increasingly important to have a proper and applicable input processing strategy.